When data is sent via a network such as a LAN (Local Area Network), the data to be sent is divided into frames at the data link layer, is relayed by a communication device, and is delivered to a destination. A layer 2 switch, for example, is known as a communication device for relaying a frame in a network in this way.
In addition, a technique for improving the reliability of a network in which ATM (Asynchronous Transfer Mode) or SDH/SONET (Synchronous Digital Hierarchy/Synchronous Optical NETwork) is used by monitoring a communication device by the use of OAM (Operations Administration Maintenance) is known (see, for example, Japanese Laid-open Patent Publication No. 2004-32633).
Furthermore, E-OAM is created by applying OAM to Ethernet (registered trademark) which is widely used in LANs, and is provided in IEEE 802.1ag or ITU-TY.1731. With E-OAM (Ethernet-OAM), in order to monitor the connectivity of a network, a MEP (Maintenance Entry Point) is set as a monitoring termination point, which is a termination node for maintenance and management, and a MIP (Maintenance Intermediate Point) is set as a monitoring intermediate point, which is a relay node for maintenance and management. A monitor group which is called a MEG (Maintenance Entity Group) and which is made up of these points is formed. An OAM frame is sent periodically and its arrival is checked. By doing so, the occurrence of a failure in the MEG can be detected.
Furthermore, with ring topology, for example, a technique for forming a physical redundant route between any communication devices in a communication network is known as a method for improving the reliability of the network. In this case, it is necessary to prevent a data frame from looping. Accordingly, STP (Spanning Tree Protocol) or the like is used for forming a spanning tree and a frame transfer control protocol is used for blocking a data frame relay via a specific port. By doing so, a communication channel between any network devices for relaying a frame is determined uniquely. When a failure has occurred, a blocking point is changed dynamically to another point. By doing so, communication can be resumed by the use of a communication channel in which a failure has not occurred.
With E-OAM, for example, it is necessary to set a MEG and MEPs and MIPs which make up the MEG. For example, however, a blocking point of data frame forwarding (transfer) in a ring network changes dynamically due to the occurrence of a failure of frame forwarding. Therefore, after the blocking point changes, the network cannot be monitored by the MEPs and the MIPs which are fixedly allocated in E-OAM. That is to say, there are cases where a blocking point is changed dynamically due to, for example, the occurrence of a failure in a network and where a termination node for data frame transfer changes. In such cases, a user or the like needs to change a termination node (MEP based on E-OAM, for example) set for monitoring according to the change in blocking point.